1. Field
The present application relates to a solid state imaging device.
2. Description of the Related Art
A solid state imaging device has pixels arranged in a 2-dimensional manner. Pixels arranged in a column direction are connected in common to a vertical signal line arranged in the column direction, and signal output from a pixel is read out to the vertical signal line. The signal read out to the vertical signal line is output to a horizontal signal line, via a horizontal selection switch arranged corresponding to the vertical signal line, and is output to the outside of the solid state imaging device, via an output section such as an output amplifier provided at an end of the horizontal signal line.
For such a solid state imaging device, a solid state imaging device employing a multi-stage hierarchical connection structure is proposed as a connection structure with regard to the horizontal signal line between the vertical signal line and the output section (for example, see patent document 1 (Japanese Unexamined Patent Application Publication No. 63-142781)). That is, the connection structure between the vertical signal line and the output section of the solid state imaging device includes two stages of horizontal signal lines (i.e., a plurality of lower stage horizontal signal lines and one upper stage horizontal signal line), and a plurality of horizontal selection switches. A plurality of vertical signal lines is associated with each one of the lower stage horizontal signal lines, and the horizontal selection switches provided to the vertical signal lines on a one-to-one basis provide connection between one of the associated lower stage horizontal signal lines and the plurality of vertical signal lines, respectively. In addition, each lower stage horizontal signal line is connected to the upper stage horizontal signal lines by horizontal selection switches provided to the lower stage horizontal signal lines on a one-to-one basis. One end of the upper stage horizontal signal line has an output section provided thereto for outputting a signal to the outside of the solid state imaging device.
In the solid state imaging device employing the multi-stage hierarchical connection structure with regard to the horizontal signal line described above, performing pixel addition (charge addition) in the horizontal direction on the horizontal signal line causes a vertical stripe to appear as noise, which essentially should not appear in the captured image, thereby resulting in degradation of the image. This will be described in detail below in a comparative example relative to the present application.
The present application has been made in view of the above circumstances, and a proposition of the application is to provide a solid state imaging device which can improve the quality of images obtained by performing pixel addition in the horizontal direction on the horizontal signal line, while employing a multi-stage hierarchical connection structure with regard to horizontal signal lines.